With latex catsuits and stockings and that sort of thing, the kind made with a sheet of latex and no hems/details, can you just cut them down? I know I'd need to be careful to prevent tears (putting in a peek-a-boo hole would probably be a bad idea) and leave wide enough areas (cutting in spaghetti straps seems like a bad idea too), but I have a catsuit I'd like to change the neckline on.

The main thing I want to do is lower the neckline by about 2-3 inches (from overbust (barely) to underbust), so the ends of the cuts would be pointing outward, as long as I did it in a smooth motion. I was thinking I'd chalk it out, put a cutting board under it, and cut it with a razor/knife/boxcutter/something good and sharp.

My only experience with rubber suggests that it tends to tear easily once you compromise its integrity. So you might find that it looks ok but tears when you put it on. You might want to figure out something will reinforce it at the line you're cutting it down to. But I have minimal experience here, so I could be wrong.

"We hurt the ones we love the most. It's a subtle form of compliment."

I asked on Fetlife as well and it was suggested I strengthen it with another layer of latex (via latex glue/cement) before cutting, but only one person answered there, so I figured I'd get second/more opinions here.

Hi Smallest,
I don't think melting would work because the material would have been "cured" (also known as vulcanizing). In other words the polymer chains are cross-linked chemically.

Once rubber is cured it will not melt, which is why you can't recycle car tyres, for example. If you heat it up it will just chemically degrade, and char.

So how to alter it with the least risk of tearing...

There are two ways to make rubber clothing. The most common way uses sheet rubber that has already been cured by a heat vulcanizing process.

The garment manufacturer buys the sheets just like a tailor would buy rolls of cloth. Then the sheets are cut into panels and then glued together using a rubber solution adhesive (one trade name for such is "copydex"). You can tell if your garment is made from rubber sheets because there will be clearly visible seams where it's been glued.

The big advantage of sheet rubber is that the thickness is very consistent. The disadvantage is the visible seams, and some latex aficionados prefer the totally smooth look.

If you go to this image and mouse-over to zoom in you will see two vertical seams.

The other way of manufacturing a garment is to make a mold of the garment and to dip it into liquid latex. The latex contains a special chemical that reacts with air and cures. This is called "air curing", and it's the way that condoms are made, for example.

Dipping is a good way to make garments that have a complex shape and tight curves. Hoods, gloves, and stockings are examples.

There's a real skill to the dipping process, and so a problem with a "bargain" dipped garment is that the thickness can be very variable, and if the latex is thin in one place it will tend to rip.

Anyway...Sebastian is correct that if you introduce any kind of weakness (like a ragged cut) into a latex garment and then stretch this part of it, it becomes a weak spot that will tear.

If you happen to cut into a seam where the glue wasn't applied properly that will create a similar weak spot.

If you have a dipped garment and happen to cut across a thinner area it will create a weak spot.

My advice:

Generally try to avoid low quality dipped garments. They are more likely to rip whether you alter them or not.

The thicker the garment generally, the less risk of tearing. Actually some latex fetishist prefer "heavy duty" garments, but these tend to have to be tailor made because thick rubber does not stretch as easily.

See if you can find a reasonably low cost garment with seams. Some leggings fall into this category. I would think it's OK to use a very sharp knife and trim the bottom of a pair of leggings (just like seamed stockings). When you do that, make sure you lubricate the cut because the knife will tend to catch with the friction. Use a water-based lube (I'm sure you have some handy ).

If you need to take, say, three inches off the garment you can start by trimming at the one-inch level to get a feel for how the knife will cut, and how best to use the lube. Then when you're more confident you can trim to the right length.

You can also try to cut with really sharp scissors. But the success of that depends on the thickness of the rubber. The thicker it is the harder you will find it is to cut.

Also if you're dealing with the manufacturer of the garment you could try dropping them an email asking for their advice on alterations.

I'm pretty sure it's made from a sheet, not dipped, but I don't have it with me (housesitting) so I'll have to look when I get home. The good thing is I wouldn't be cutting on a seam, if there are any. It would be pretty well front and center on the garment.